In an electrical converter, the commutation loop stray inductance causes voltage overshoots during switching, produces EMI emissions by ringing, and increases the switching losses. Furthermore, experience with wide bandgap semiconductor power modules shows that the ringing in the power circuit may also produce high frequency noise in the gate circuit, thereby decreasing the controllability of the semiconductor switches and requiring a more sophisticated gate driver. The power module may be part of the commutation loop, therefore minimizing its stray inductance may be important.
Furthermore, power modules for fast switching semiconductors, especially for wide bandgap semiconductors, should have a low stray inductance (below 10 nH) to handle short current rise-times. On the other hand, a low current rating of typical wide bandgap semiconductors usually requires electrical paralleling of many semiconductor chips to reach practical current levels. Paralleling of semiconductor chips, however, requires more space for chip placement and signal routing and may therefore result in a higher stray inductance.
The stray inductance of a power module may be to a large part caused by the design of its power terminals. One reason may be the larger creepage and clearance distances required for external parts of the power terminals, where there may be no encasing (for example made of Si-Gel or epoxy). However, also with optimizing the internal structure of the power module, a lower stray inductance may be gained.
US 2005/0024805 A1 relates to a low inductance circuit arrangement for power semiconductor modules, in which a low-inductive power module assembly using terminal stripline and ribbon bonds is described.
DE 10 2014 102 018 B3 relates to a power module with a low stray inductance by a special arrangement of wire bonds.
U.S. Pat. No. 5,705,848 relating to a power semiconductor module describes a low-inductive and space-efficient way of interconnecting substrates using floating plates.